<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .pink {
            background-color: pink;
        }
    </style>
</head>

<body>
    <button class="pink">按钮1</button>
    <button>按钮2</button>
    <button>按钮3</button>
    <button>按钮4</button>
    <script>
        let bts = document.querySelectorAll('button');
        for (let i = 0; i < bts.length; i++) {
            bts[i].addEventListener('click',function(){
                document.querySelector('.pink').className=''
                this.className='pink'
            })
        }
    </script>
</body>

</html>